Multi-wheel-driving vehicle

ABSTRACT

A multi-wheel-driving vehicle including at least three parallel axles each of which is provided on both ends thereof with respective drive wheels and including power dividing means for permitting the rotary speed among the axles, is improved in its effect of braking so that the braking force of fewer brakes is effectively transmitted to all drive wheels of a vehicle according to a simple braking operation by a driver. The power dividing means, for example, a differential gear unit, includes an input member and a pair of output members, like differential side gears, each of which interlocks with at least one of the axles so as to differentially share a driving force received by the input member between the pair of output members. The multi-wheel-driving vehicle comprises a brake provided on one of the at least three axles, and locking means for locking the input member and the pair of output members together, so that when a driver operates a brake-operating tool for braking, the locking means is automatically operated to lock the input member and the pair of output members together.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT

[0002] Not applicable

REFERENCE TO MICROFICHE APPENDIX/SEQUENCE LISTING/TABLE/COMPUTER PROGRAMLISTING APPENDIX Submitted on a Compact Disc and anIncorporation-By-Reference of the Material on the Compact Disc

[0003] Not applicable.

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] The present invention relates to a multi-wheel-driving vehicleprovided with not less than six drive wheels. More particularly, thepresent invention relates to a technique for improving the brakingcapacity of the multi-wheel-driving vehicle, as well as compactness andcost savings in its construction.

[0006] 2. Background Art

[0007] Conventionally, there is a multi-wheel-driving vehicle havingthree or more axles disposed in parallel, each of which is provided atits left and right ends with respective drive wheels. Generally, eachaxle is divided into left and right halves which are differentiallyconnected with each other through a differential.

[0008] U.S. Pat. No. 4,050,534 discloses a power transmission system forsuch a multi-wheel-driving vehicle wherein engine power is distributedamong three axles as follows. The torque output from a transmission isfirstly transmitted to a tandem axle mechanism, i.e., a centerdifferential which differentially connects a pair of coaxial first andsecond transmission shafts. The tandem axle mechanism distributes a partof the torque to the frontmost (steerable) axle and the rearmost axlethrough the first transmission shaft and the remainder of the torque tothe middle axle (second rear axle) through the second transmissionshaft, thereby nicely balancing the torque among the three axles.However, in such a cited conventional power distribution structure, thefrontmost axle for steerable front drive wheels is drivinglysynchronized with the rearmost axle for unsteerable rear drive wheels,so that the driving of the front wheels is restricted while turning bythe driving of the rear wheels, thereby hindering a smooth steering ofthe vehicle. For avoiding such a problem, it is effective to have theaxle of the steerable wheels drivingly differentially connected with theother axles.

[0009] Furthermore, this cited document does not disclose an arrangementof brakes. In the cited art, if only the middle axle of the three isprovided thereon with a brake, the tandem axle mechanism prevents thebraking force applied thereon from being effectively transmitted to thefrontmost and rearmost axles. On the other hand, if a brake is justprovided on either the front axle or the rearmost axle, the brakingforce applied on the axle is transmitted to the other of the front orrearmost axle because the two axles interlock with each other throughthe first transmission shaft. However, the braking force is noteffectively transmitted to the middle axle interlocking with the secondtransmission shaft. Thus, to effectively stop the vehicle, the middleaxle and at least one of the frontmost and rearmost axles needrespective brakes, whereby at least two brakes are necessary.

[0010] Furthermore, as mentioned above, each axle is generally dividedinto two halves differentially connected with each other. If only one ofthe halves is provided thereon with a brake, the braking force cannot beeffectively transmitted to the other half. If the first and secondtransmission shafts of the tandem axle mechanism are locked together andif the halves of each axle are locked together, a braking forcegenerated by fewer brakes can be effectively transmitted to all axles,thereby improving compactness of the vehicle and increasingcost-savings. It is preferable that such differential-locking operationsare automatically performed due to the driver's braking operation so asto facilitate the driver's work.

BRIEF SUMMARY OF THE INVENTION

[0011] A first object of the present invention is to provide amulti-wheel-driving vehicle including three or more axles arranged inparallel along a longitudinal axis of the vehicle. Each of the axles isprovided on each end thereof with a respective drive wheel. One of thethree or more axles is a steering axle provided with steerable drivewheels, and includes power dividing means for permitting rotary speedamong the axles, wherein the steering axle is drivingly differentiallyconnected with the other axles so that the steerable drive wheels can bedriven while receiving nicely distributed power.

[0012] To achieve the first object, the vehicle is provided with a pairof transmission members like coaxial shafts between which a first powerdividing means, such as a one-way clutch, is interposed. The steeringaxle synchronously interlocks with one of the transmission members, andat least another axle, preferably, all the axles other than the steeringaxle interlock with the other transmission member. Power is transmittedthrough the first power dividing means between both the transmissionmembers while the first power dividing means allows a difference ofrotary speed between the transmission members.

[0013] Alternatively, the vehicle is provided with a second powerdividing means, such as a differential, comprising an input member and apair of output members (like coaxial shafts) provided thereon withrespective differential side gears. Each of the output memberssynchronously interlocks with at least one axle. The steering axlesynchronously interlocks with either the input member or one of theoutput members of the second power dividing means. Preferably, only thesteering axle of the three or more axles synchronously interlocks withone of the output members. At least one axle other than the steeringaxle interlocks with the other output member. The remaining axle oraxles interlock with either the input member or the other output member.

[0014] Furthermore, three or more transaxle devices may be arranged intandem along the longitudinal axis of the vehicle so that each of thetransaxle devices includes input means and each of the three or moreaxles serves as output means. One of the three or more transaxle devicesis a main transaxle device whose input means receives power from a primemover prior to the other transaxle devices. Another of the transaxledevices is a steering transaxle device whose axle is the steering axle.Preferably, the steering transaxle device is separate from the maintransaxle device.

[0015] In this case, a continuous variable transmission may beinterposed between the prime mover and the input means of the maintransaxle device. If the input means is provided on one side of the maintransaxle device, a power-take-out portion of the main transaxle devicefor transmitting power to another transaxle device may be provided onanother opposite side of the main transaxle device.

[0016] If the power dividing means is the above-mentioned first powerdividing means interposed between a pair of first and secondtransmission members for transmitting power from the first transmissionmember to the second transmission member, the input means of the maintransaxle device synchronously interlocks with the first transmissionmember, and at least one input means of the other transaxle devicessynchronously interlocks with the second transmission member.Preferably, only the axle of the steering transaxle device synchronouslyinterlocks with the second transmission member, and all the axles of theother transaxle devices synchronously interlock with the firsttransmission member.

[0017] If the power dividing means is the second power dividing meansincluding the input member and the pair of output members, power takenfrom the main transaxle device is transmitted into the input member ofthe second power dividing means. Each of all the input member and theoutput members of the second power dividing means synchronouslyinterlocks with at least one of all the axles of the three or moretransaxle devices. Alternatively, all the axles of the three or moretransaxle devices may distributively synchronously interlock with thepair of output members of the second power dividing means so that atleast one axle synchronously interlocks with each of the output membersof the second power dividing means. Preferably, only the steering axlesynchronously interlocks with one of the output members of the secondpower dividing means.

[0018] A second object of the present invention is to provide themulti-wheel-driving vehicle as mentioned above with a braking force,supplied by fewer brakes, that is effectively transmitted to all drivewheels of a vehicle in response to a simple braking operation by adriver, thereby enhancing braking effectiveness and reducing the cost ofproviding brakes.

[0019] To achieve the second object, a brake such as a wet-type isprovided on one of the three or more axles. In the case that the threeor more axles serve as output means of respective transaxle deviceincluding input means, a brake is provided on a transmission system orthe axle in the main transaxle device. If the first power dividing meansis utilized, locking means is provided for locking the pair oftransmission members together, so that when a driver operates a manualbrake-operating tool for braking, the locking means is automaticallyoperated to lock the pair of transmission members together.

[0020] If the second power dividing means is utilized, locking means isprovided for locking the input member and the pair of output memberstogether, so that when the driver operates the brake-operating tool forbraking, the locking means is automatically operated to lock the inputmember and the pair of output members together.

[0021] Additionally, if the axle provided thereon with the brake isdivided into two halves differentially connected with each other througha differential and the brake is provided on one of the halves,differential-locking means is provided for locking the two halvestogether. Thus, when a driver operates the brake-operating tool forbraking, the differential-locking means is automatically operated tolock the halves together.

[0022] Other and further objects of the present invention will appearmore fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0023]FIG. 1 is a schematic diagram of a driving transmission system ofa multi-wheel-driving vehicle including front, middle and rear transaxledevices disposed in tandem along a longitudinal axis of the vehicleaccording to a first embodiment of the present invention.

[0024]FIG. 2 is a schematic diagram of the rear transaxle device of thesame multi-wheel-driving vehicle;

[0025]FIG. 3 is a sectional developed view of the interior of the reartransaxle device;

[0026]FIG. 4 is a schematic diagram of the middle transaxle device ofthe same multi-wheel-driving vehicle;

[0027]FIG. 5 is a sectional plan view of the interior of the middletransaxle device;

[0028]FIG. 6 is a sectional side view of the same;

[0029]FIG. 7 is a schematic diagram of the front transaxle device of thesame multi-wheel-driving vehicle;

[0030]FIG. 8 is a hydraulic and electric circuit diagram of a controlsystem for brakes and clutches in the driving transmission system of thesame multi-wheel-driving vehicle;

[0031]FIG. 9 is a schematic diagram of a driving transmission system ofa multi-wheel-driving vehicle according to a second embodiment of thepresent invention;

[0032]FIG. 10 is a schematic diagram of a driving transmission system ofa multi-wheel-driving vehicle according to a third embodiment of thepresent invention;

[0033]FIG. 11 is a hydraulic and electric circuit diagram of a controlsystem for braking and differential-locking in the driving transmissionsystem of the multi-wheel-driving vehicle according to the thirdembodiment;

[0034]FIG. 12 is a schematic diagram of a driving transmission system ofa multi-wheel-driving vehicle according to a fourth embodiment of thepresent invention;

[0035]FIG. 13 is a schematic diagram of a driving transmission system ofa multi-wheel-driving vehicle according to a fifth embodiment of thepresent invention;

[0036]FIG. 14 is a schematic diagram of a driving transmission system ofa multi-wheel-driving vehicle according to a sixth embodiment of thepresent invention, and

[0037]FIG. 15 is a schematic diagram of a driving transmission system ofa multi-wheel-driving vehicle according to a seventh embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0038] Referring to FIG. 1, a multi-wheel-driving vehicle 1 comprises afront transaxle device 10 which serves as a steering transaxle devicedisposed at its front portion, a middle transaxle device 16 disposed atits longitudinally intermediate portion, and a rear transaxle device 4disposed at its rear portion. Rear transaxle device 4 which serves as amain transaxle device includes a pair of left and right rear axles 8serving as main axles which support at their outer ends respective rearwheels 9. Middle transaxle device 16 includes a pair of left and rightmiddle axles 25 serving as second axles which support at their outerends respective middle wheels 26. Front transaxle device 10 includes apair of left and right front axles 11 serving as steering axles whichsupport at their outer ends respective steerable front wheels 12.

[0039] The power of an engine 3, which serves as a prime mover mountedon a body of multi-wheel-driving vehicle 1, is transmitted to rear axles8 of rear transaxle device 4 so as to drive rear wheels 9 forward andbackward, thereby making vehicle 1 travel forward and backward. Also, afour-wheel-drive mode in which middle wheels 26 are driven in additionto rear wheels 9 or a six-wheel-drive mode in which front wheels 12 arestill additionally driven can be selectively established by a driver'soperation.

[0040] A transmission system for transmitting power from engine 3 torear axles 9 comprises a continuous variable transmission (hereinafter,“CVT”) 7 disposed outside rear transaxle device 4 and a speed-changinggear transmission 35 disposed in rear transaxle device 4. CVT 7 isinterposed between an output shaft 6 of engine 3 and an input shaft 5 ofspeed-changing gear transmission 35. Input shaft 5 projects laterallyoutwardly from one of left and right sides of a rear axle housing 31 ofrear transaxle device 4. A follower split pulley 36 is provided on inputshaft 5 outside housing 31 for constituting CVT 7.

[0041] In this embodiment, CVT 7 is a belt-type CVT constituted by splitpulleys and a belt wherein the speed reduction ratio is automaticallysteplessly reduced according to the increase of rotary speed of engine3. However, it may be replaced with a hydrostatic stepless transmissionincluding a hydraulic pump and a hydraulic motor, for example, which ismanually or automatically adjusted in its output rotary speed. Anytransmission mechanism may be interposed between output shaft 6 andinput shaft 5 if it agrees with the requirements.

[0042] Description will be given on rear transaxle device 4 withreference to FIGS. 2 and 3. Rear axle housing 31 of rear transaxledevice 4 is made of a pair of left and right housing halves joinedtogether. In housing 31 are laterally disposed a drive shaft 37, acounter shaft 41 and coaxial rear axles 8 in parallel to one another.Drive shaft 37 is coaxially connected to input shaft 5 through a torquesensor 34. Torque sensor 34 detects various type resistances such asrolling resistance, air resistance, acceleration resistance and graderesistance generated from each of wheels 12, 26 and 9 or the like, andoutputs detection signals into a controller (not shown). The controlleradjusts the degree of opening of a throttle valve of engine 3correspondingly to the detection signals, thereby serving as a torquesensing governor.

[0043] In housing 31 is interposed a speed-changing gear transmission 33between drive shaft 37 and counter shaft 41. Drive shaft 37 is fixedlyprovided therearound with a high-speed drive gear 38 and a low-speeddrive gear 39, and notched on its periphery so as to integrally form areverse drive gear 40. A high-speed follower gear 42 and a reversefollower gear 44 are relatively rotatably provided around counter shaft41. High-speed follower gear 42 directly engages with high-speed drivegear 38. Reverse follower gear 44 engages with reverse drive gear 40through an idle gear 45. A low-speed follower gear 43 is relativelyrotatably provided around a boss portion of high-speed follower gear 42so as to directly engage with low-speed drive gear 39.

[0044] A spline hub 46 is fixedly disposed around counter shaft 41between low-speed follower gear 43 and reverse follower gear 44. Agear-changing clutch slider 47 is axially slidably but not relativelyrotatably disposed around spline hub 46. Gear-changing clutch slider 47is axially slidden along counter shaft 41 so as to engage with one ofgears 42, 43 and 44 provided on counter shaft 41, thereby selectivelybringing counter shaft 41 into a high-speed regularly directed rotation,a low-speed regularly directed rotation or a reversely directedrotation. Also, gear-changing clutch slider 47 can be located at itsneutral position where it does not engage with any of gears 42, 43 and44.

[0045] Vehicle 1 is provided with a manually operable speed-changingtool (not shown) such as a lever interlocking with gear-changing clutchslider 47. The speed-changing tool is shiftable among a high-speedforward driving position, a low-speed forward driving position, areverse driving position and a neutral position, thereby slidinggear-changing clutch slider 47 correspondingly.

[0046] Counter shaft 41 is notched on its periphery so as to form anoutput gear 51 adjacent to one of its ends. Output gear 51 constantlyengages with a ring gear 53 of a main-axle-differential 32 which isdisposed in rear axle housing 31 for differentially connecting left andright coaxial rear axles 8 with each other.

[0047] Main-axle differential 32 will be described. A hollowdifferential casing 52 is disposed coaxially with rear axles 8 androtatably supported by housing 31. Ring gear 53 serving as an input gearof the main-axle-differential 32 is fixed around differential casing 52so as to engage with output gear 51. In differential casing 52, a pinionshaft 54 is disposed between facing inner ends of rear axles 8 andperpendicularly to rear axles 8, and is supported by differential casing52 so as to be rotatable together with differential casing 52 centeringaxes of rear axles 8. Pinion shaft 54 is rotatably provided thereon witha pair of pinions 55 adjacent to differential casing 52 into which eachof the ends of pinion shaft 54 is engaged. In differential casing 52,differential side gears 56 are fixedly disposed on respective rear axles8 symmetrically with respect to pinion shaft 54 so as to engage withboth pinions 55.

[0048] A main-axle-differential locking mechanism 33 for lockingmain-axle-differential 32 together with both rear axles 8 will bedescribed. The portion of differential casing 52 laterally opposite toring gear 53 is formed into a boss. A main-axle-differential lockingslider 57 is axially slidably disposed around the boss portion ofdifferential casing 52. At least one lock pin 58 is fixed at one endthereof to main-axle-differential locking slider 57 and projects at theother end thereof into differential casing 52 in parallel to rear axles8. The differential side gear 56 disposed adjacent tomain-axle-differential locking slider 57 is provided at its surfacedirected toward main-axle-differential locking slider 57 with a recess59 into which lock pin 58 can be engaged. When differential-lockingslider 52 is slidden along the boss portion of differential casing 52toward main-axle-differential 32, lock pin 58 is moved together withmain-axle differential-locking slider 57 and engaged into recess 59 soas to lock main-axle-differential 32 together with both rear axles 8,thereby making both rear axles 8 rotate at the same rotary speed.

[0049] Vehicle 1 is provided with a manually operabledifferential-locking tool (not shown) such as a lever interlocking withmain-axle-differential locking slider 57. The differential-locking toolis switchable between a locking position and an unlocking position,thereby selectively locking or unlocking main-axle-differential 32.

[0050] A hydraulic brake 22 of a wet multi-frictional-disc type isprovided on each rear axle 8 in housing 31. As shown in FIG. 8 (asdiscussed below), vehicle 1 is provided with a brake pedal 19 which isdepressed so as to simultaneously apply brake force onto both rear axles8 through brakes 22.

[0051] A PTO casing 15 is fixedly mounted on an outer side surface ofrear axle housing 31 in laterally opposite to input shaft 5. In rearaxle housing 31, counter shaft 41 is extended at its one end outwardlyand coaxially connected to an extension shaft 61 through a coupling 60.Extension shaft 61 projects into PTO casing 15. A first PTO shaft 63projects forward from PTO casing 15. In PTO casing 15, a bevel gear 62fixed on extension shaft 61 engages with a bevel gear 64 fixed on firstPTO shaft 63.

[0052] Description will be given on middle transaxle device 16 withreference to FIGS. 4 through 6. An input shaft 82 is disposedlongitudinally of vehicle 1, rotatably supported by a middle axlehousing 16 a, and projects backward from housing 16 a so as to beuniversally joined with first PTO shaft 63 through a propeller shaft 17.In middle axle housing 16 a, a clutch gear 86 is fixedly provided aroundinput shaft 82. A counter shaft 83 is rotatably disposed parallel toinput shaft 82 in middle axle housing 16 a, and fixedly provided thereonadjacent to its rear end with a counter gear 84 which constantly engageswith clutch gear 86. A front end of counter shaft 83 is formed into abevel gear 85.

[0053] Coaxial left and right middle axles 25 are differentiallyconnected with each other through a second-axle-differential 89 inmiddle axle housing 16 a. Second-axle-differential 89 for middle axles25, similar to main-axle-differential 32 for rear axles 8, comprises adifferential casing 91, a pinion shaft 92, a pair of pinions 93 and apair of differential side gears 94. Differential casing 91 is disposedcoaxially with middle axles 25 and rotatably supported by middle axlehousing 16 a. A bevel gear 90 serving as an input gear ofsecond-axle-differential 89 is fixed around differential casing 91 so asto constantly engage with bevel gear 85. Pinion shaft 92 is disposedbetween middle axles 25 and perpendicularly to middle axles 25 indifferential casing 91 and supported at its opposite ends bydifferential casing 91. Pinions 93 are rotatably provided around pinionshaft 92 in differential casing 91 so as to be disposed symmetricallywith respect to middle axles 25. In differential casing 91 are disposedinner ends of middle axles 25 around which differential side gears 94are respectively fixed so as to engage with both pinions 93.

[0054] A second PTO shaft 87 is disposed in middle axle housing 16 acoaxially with input shaft 82 and projects forward therefrom. In middleaxle housing 16 a, a front end of input shaft 82 is backwardly recessedand a rear end of second PTO shaft 87 is inserted into the recessedfront end of input shaft 82. A one-way clutch 20 is interposed betweeninput shaft 82 and second PTO shaft 87. One-way clutch 20 is engaged soas to transmit driving force therebetween only when input shaft 82 isrotated for forward driving of vehicle 1. On the other hand, one-wayclutch 20 is disengaged so as to allow a difference in rotary speedbetween input shaft 82 and second PTO shaft 87, that is, between middlewheels 26 and front wheels 12. A center clutch slider 88 is axiallyslidably disposed around second PTO shaft 87. A center clutch isconstructed between center clutch slider 88 and clutch gear 86 so as tobe engaged and disengaged by sliding of center clutch slider 88.

[0055] In this embodiment, middle transaxle device 16 includingsecond-axle-differential 89 is constantly drivingly connected with reartransaxle device 4 including main-axle-differential 32. In the case thata front clutch for drivingly connecting front transaxle device 10 tomiddle transaxle device 16 is engaged, when center clutch slider 88 isslidden backward so as to engage the center clutch, that is, to lockinput shaft 82 and second PTO shaft 87 together regardless of one-wayclutch 20, middle transaxle device 16 and front transaxle device 4 canbe drivingly synchronized with each other, thereby enabling front wheels12 to be driven synchronously with middle wheels 26 and rear wheels 9.

[0056] With reference to FIG. 7, description will be given on fronttransaxle device 10. An input shaft 14 is disposed longitudinally ofvehicle 1, rotatably supported by a front axle housing 10 a, andprojects backward so as to be connected to second PTO shaft 87 through apropeller shaft 18 and universal joints. In front axle housing 10 a is afront clutch shaft 95 coaxially disposed with input shaft 14. A frontclutch slider 96 is axially slidably disposed around front clutch shaft95. A front clutch is constructed between the rear end of front clutchslider 96 and the front end of input shaft 14 so as to be engaged anddisengaged by sliding of front clutch slider 96. Front clutch shaft 95is fixedly provided at its front end with a bevel gear 97 so as toconstantly engage with a bevel gear 98 serving as an input gear of athird-axle-differential 99 which differentially connects coaxial leftand right front axles 11 with each other.

[0057] Third-axle-differential 99 is constructed almost similarly withmain-axle-differential 32 of rear transaxle device 4 andsecond-axle-differential 89 of middle transaxle device 16. The maindifference is that third-axle-differential 99 for front axles 11 isprovided in its differential casing with multiple frictional discs,thereby serving as a multi-disc-type limited slip differential.

[0058] Description will now be given on a control system for brakes 22and clutch sliders 88 and 96 in accordance with FIG. 8, wherein clutchsliders 88 and 96 are operated so as to effectively transmit the brakingforce generated by brakes 22 in rear transaxle device 4 to middle andfront transaxle devices 16 and 10.

[0059] Brake pedal 19 is hydraulically connected to the pair of brakes22 in rear transaxle device 4 through a hydraulic circuit 100 whichcomprises a master cylinder 101, an oil tank 102, an oil filter 103, amanual valve 104 and an oil passage 105. Oil is supplied from oil tank102 into master cylinder 101 through oil filter 103 and valve 104. Oilpassage 105 is extended from a discharge port of master cylinder 101 andbranches to both brakes 22.

[0060] Master cylinder 101 is provided therein with a piston 107 and aspring 108 biasing piston 107 to the initial position. A piston rod 106is fixedly extended from piston 107 opposite of the discharge port ofmaster cylinder 101 so as to be connected to brake pedal 19. Brake pedal19 is depressed so as to push piston 107 toward the discharge port ofmaster cylinder 101 through piston rod 106 as much as the degree ofdepression of brake pedal 19, thereby discharging oil from mastercylinder 101 into both brakes 22 through oil passage 105 and pressingthe multi-discs of each brake 22 against one another so as to brake bothrear axles 8. When brake pedal 19 is depressed beyond a predetermineddegree, valve 104 is closed so as to stop oil supply into mastercylinder 101, thereby preventing oil from back-flowing to oil tank 102and ensuring the action of piston 107 according to depression of brakepedal 19. When brake pedal 19 is released from the depressing forceapplied thereon, piston 107 and brake pedal 19 are returned to theirinitial position by the biasing force of spring 108.

[0061] A switching sensor 48 is disposed adjacent to brake pedal 19 soas to be switched on by depression of brake pedal 19. Switching sensor48 is electrically connected to a controller 30 for controlling theengaging and disengaging of the above-mentioned clutches.

[0062] A center clutch lever 121 is disposed beside a driver's seat ofvehicle 1 for operating center clutch slider 88 disposed in middletransaxle device 16. A switching sensor 49 is disposed so as to beswitched on when center clutch lever 121 is located at its clutch-onposition. A front clutch lever 122 is also disposed beside the driver'sseat for operating front clutch slider 96 disposed in front transaxledevice 10. A switching sensor 50 is disposed so as to be switched onwhen front clutch lever 122 is located at its clutch-on position. Bothswitching sensors 49 and 50 are electrically connected to controller 30so as to send signals about the positions of levers 121 and 122 tocontroller 30.

[0063] A hydraulic circuit 120 for sliding clutch sliders 88 and 96comprises a hydraulic pump 110 driven by engine 3, an oil tank 111 forsupplying oil to hydraulic pump 110, a pair of hydraulic cylinders 112serving as a double actuator for sliding center clutch slider 88, a pairof hydraulic cylinders 113 serving as a double actuator for slidingfront clutch slider 96, a solenoid valve 114 for hydraulicallycontrolling cylinders 112, a solenoid valve 115 for hydraulicallycontrolling cylinders 113, and a relief valve 116 for controlling thehydraulic pressure in hydraulic circuit 120.

[0064] Pistons of both cylinders 112 are fixed to each other and coupledwith center clutch slider 88. Solenoid valve 114 is switched between twopositions, in each position oil discharged from hydraulic pump 110 issupplied into one of cylinders 112 and simultaneously oil is drainedfrom the other cylinder 112, thereby shifting center clutch slider 88between a clutch-on position and a clutch-off position. The same is truefor cylinders 113 and solenoid valve 115 regarding the front clutchcomprising front clutch slider 96.

[0065] When brake pedal 19 is not depressed, switching sensor 48 is off,whereby solenoid valves 114 and 115 are controlled by controller 30 soas to locate each of clutch sliders 88 and 96 between its clutch-onposition and its clutch-off position according to the positions ofcenter clutch lever 121 and front clutch lever 122 which are detected byswitching sensors 49 and 50. When brake pedal 19 is depressed, switchingsensor 48 is switched on so that both solenoid valves 114 and 115 arecontrolled by controller 30 so as to forceably locate both clutchsliders 88 and 96 at their clutch-on positions regardless of thepositions of levers 121 and 122.

[0066] Due to such a control system, when brakes 22 are operated forbraking, the three transaxle devices 4, 16 and 10 are drivinglyconnected together so as to make the braking force applied onto rearaxles 8 effectively transmitted to middle axles 25 and front axles 8,whereby all of the six wheels 9, 26 and 12 are braked, therebyshortening the braking distance of vehicle 1.

[0067] Alternatively, during the depression of brake pedal 19, onlysolenoid valve 114 may be forceably controlled for locating centerclutch slider 88 to its clutch-on position so that rear wheels 9 andmiddle wheels 26, four wheels in total, are braked.

[0068] Description will now be given on various driving transmissionsystems as modifications of the above-mentioned first preferredembodiment. Referring to a second embodiment shown in FIG. 9, instead ofone-way clutch 20, a center differential 23 is interposed between inputshaft 82 and second PTO shaft 87 in middle transaxle device 16 forsharing the torque transmitted from rear transaxle device 4 betweenfront transaxle device 10 and middle transaxle device 16, therebypermitting a difference in rotary speed between front wheels 12 andmiddle wheels 26. Center differential 23 differentially connects bothshafts 82 and 87 with each other. Input shaft 82 is inserted into adifferential casing 23 a of center differential 23 so as to makedifferential casing 23 a integrally rotatable with input shaft 82. Indifferential casing 23 a are disposed a pair of differential side gears23 b and 23 c and a pair of differential pinions 23 d. Differential sidegear 23 b is rotatably provided around input shaft 82 and is formedintegral with clutch gear 86 disposed outside differential casing 23 awhile differential side gear 23 c is fixed to second PTO shaft 87.Differential pinions 23 d are interposed between differential side gears23 b and 23 c in typical form.

[0069] A center differential locking clutch slider 88′ replacing centerclutch slider 88 is axially slidably provided around input shaft 82. Acenter differential locking clutch is constructed between clutch gear 86and center differential locking clutch slider 88′ so as to be engagedand disengaged by sliding of center differential locking clutch slider88′. When center differential locking clutch slider 88′ is located so asto engage the center differential locking clutch, clutch gear 86 andinput shaft 82 are joined together so as to drivingly synchronize middletransaxle device 16 and rear transaxle device 4 with each other, andalso, center differential 23 is locked together with both shafts 82 and87, whereby front transaxle device 10 is synchronously driven withmiddle and rear transaxle devices 16 and 4 if the front clutch isengaged.

[0070] When brake pedal 19 is depressed so as to switch on switchingsensor 48, center differential locking clutch slider 88′ and frontclutch slider 96 are forceably located at their clutch-on positions fortransmitting braking force applied on rear axles 8 to middle and frontaxles 25 and 11. Other undescribed parts of this second embodiment aresimilar with those of the first embodiment.

[0071] Referring to a third embodiment shown in FIG. 10, centerdifferential 23 and the center differential locking clutch are disposedin middle transaxle device 16 similar to the second embodiment. In reartransaxle device 4, only one brake 22 is disposed on one of left andright rear axles 8.

[0072] The third embodiment employs a control system for operation ofthe front clutch and differential-locking of main-axle-differential 32and center differential 23 as shown in FIG. 11, wherein the front clutchare engaged and main-axle-differential 32 and center differential 23 aredifferentially locked so as to effectively transmit the braking forcegenerated by single brake 22 in rear transaxle device 4 to middle andfront transaxle devices 16 and 10.

[0073] Beside the driver's seat of vehicle 1 are provided a centerdifferential locking lever 121′ replacing center clutch lever 121, and amain-axle-differential locking lever 125. Each of differential lockinglevers 121′ and 125 is shiftable between its locking position and itsunlocking position. A switching sensor 49′ is provided so as to beswitched on when center differential locking lever 121′ is located atits locking position. A switching sensor 65 is provided so as to beswitched on when main-axle-differential locking lever 125 is located atits locking position.

[0074] In a hydraulic circuit 120′ for operating sliders 57, 88′ and 96,the pair of hydraulic cylinders 112 are provided for sliding centerdifferential locking clutch slider 88′ between its locking and unlockingpositions, and solenoid valve 114 is provided for controllingoil-supplying and oil-draining of cylinders 112. Additionally, a pair ofhydraulic cylinders 123 serve as a double actuator for slidingmain-axle-differential locking slider 57 between its locking andunlocking positions. A solenoid valve 124, electrically connected tocontroller 30, is provided for controlling oil-supplying andoil-draining of cylinders 123. Other structures and parts are similarwith those of hydraulic circuit 120 shown in FIG. 8.

[0075] Further, the controlling parts for main-axle-differential lockingmechanism 33 such as main-axle-differential locking lever 125, hydrauliccylinders 123 and solenoid valve 124 are also provided in the controlsystem of the first embodiment shown in FIG. 8. These features areomitted in FIG. 8 because they are irrelevant to the description of theclutch-controlling for effectively transmitting braking force to allwheels 9, 26 and 12 of vehicle 1.

[0076] In the third embodiment, the forced controlling ofmain-axle-differential locking mechanism 33 is required for transmittingthe braking force of only one brake 22 to both rear axles 8. Therefore,in this embodiment, when brake pedal 19 is depressed, solenoid valves114, 115 and 124 are controlled by controller 30 so as to forceablylocate main-axle-differential locking slider 57, center differentiallocking clutch slider 88′ and front clutch slider 96 at their locking orclutch-on positions. Thus, the braking force generated by only one brake22 provided on one rear axle 8 can be effectively transmitted to theother rear axle 8 and also transmitted to both middle wheels 26 and bothfront wheels 12, thereby effectively stopping vehicle 1.

[0077] Four preferred embodiments shown in FIGS. 12 to 15, whereinmiddle axles 25 serves as main axles and rear axles 8 serves as secondaxles, have such a common structure as follows. Power of engine 3 is,first, transmitted to middle transaxle device 16 serving as a maintransaxle device, and driving force is transmitted from middle transaxledevice 16 to rear transaxle device 4 and front transaxle device 10.Speed-changing gear transmission 35, torque sensor 34,main-axle-differential 32 and main-axle-differential locking mechanism33 are exchanged with second-axle-differential 89 between rear transaxledevice 4 and middle transaxle device 16. Main-axle-differential 32differentially connects coaxial left and right middle axles 25 with eachother. Only one of middle axles 25 is provided thereon with brake 22.Second-axle-differential 89 differentially connects coaxial left andright rear axles 8 with each other. Rear transaxle device 4 is providedwith a forwardly extended input shaft 13 which receives driving forcetransmitted from middle transaxle device 16.

[0078] In each of the embodiments shown in FIGS. 12 through 15 (exceptfor that shown in FIG. 14), middle transaxle device 16 is provided onone outer side of its middle axle housing 16 a, preferably in oppositeto its input side, with a PTO casing 15′ replacing PTO casing 15. A rearPTO shaft 82′ is extended backward from PTO casing 15′ so as to beuniversally joined to input shaft 13 of rear transaxle device 4 throughpropeller shaft 17. A front PTO shaft 87′ is extended forward from PTOcasing 15′ so as to be universally joined to input shaft 14 of fronttransaxle device 10 through propeller shaft 18.

[0079] Referring to a fourth embodiment shown in FIG. 12, counter shaft41 (or extension shaft 61 coaxially extended from counter shaft 41)projects into PTO casing 15′. In PTO casing 15′, a bevel gear 28 fixedto counter shaft 41 constantly engages with a bevel gear 27 fixed torear PTO shaft 82′. Rear PTO shaft 82′ and front PTO shaft 87′ aredisposed coaxially with each other. One-way clutch 20 is interposedbetween rear PTO shaft 82′ and front PTO shaft 87′, thereby permitting adifference of rotary speed therebetween. Center clutch slider 88 isaxially slidably disposed around front PTO shaft 87′. A center clutch isconstructed between center clutch slider 88 and bevel gear 27 fixed torear PTO shaft 82′.

[0080] In this embodiment, due to such a structure, rear transaxledevice 4 is constantly drivingly connected with middle transaxle device16. When the center clutch is engaged while the front clutch in fronttransaxle casing 10 is engaged, front transaxle device 10 is alsosynchronously driven with middle and rear transaxle devices 16 and 4.

[0081] The fourth embodiment employs a similar control system as shownin FIG. 8 so that, when brake pedal 19 is depressed, both the centerclutch including center clutch slider 88 and the front clutch includingfront clutch slider 96 are forceably engaged for effectivelytransmitting braking force from one middle axle 25 serving as a mainaxle to rear axles 8 serving as second axles and front axles 11 servingas steering axles. However, for effectively braking all wheels ofvehicle 1, in addition to that shown in FIG. 8, main-axle-differentiallocking slider 57 is required to be forceably slidden so as to lockmain-axle-differential 32 as shown in FIG. 11.

[0082] Referring to a fifth embodiment shown in FIG. 13, in middle axlehousing 16 a of middle transaxle device 16, a second counter shaft 71and a third counter shaft 72 are disposed parallel to counter shaft 41and middle axles 25. Third counter shaft 72 is extended into PTO casing15′ so as to engage with rear PTO shaft 82′ through bevel gears. Adifferential output shaft 73 is disposed coaxially with second countershaft 71 and extended into PTO casing 15′ so as to engage with front PTOshaft 87′ through bevel gears.

[0083] In middle axle housing 16 a, center differential 23′ isinterposed between second counter shaft 71 and differential output shaft73 so as to differentially connecting both shafts 71 and 73 with eachother. Output gear 51, fixedly provided on counter shaft 41, constantlyengages with a ring gear 74 of center differential 23′ so that thetorque of counter shaft 41 is transmitted to center differential 23′ andshared between second counter shaft 71 and differential output shaft 73.

[0084] Center differential locking clutch slider 88′ is axially slidablydisposed around second counter shaft 71 so as to engage with anddisengage from a differential casing 23′a of center differential 23′.When center differential locking clutch slider 88′ is slidden to engagewith differential casing 23′a, center differential 23′ is locked so asto lock second counter shaft 71 and differential output shaft 73together.

[0085] A middle-axle-drive gear 75 fixed on second counter shaft 71constantly engages with ring gear 53 of main-axle-differential 32differentially connecting middle axles 25 with each other. A firstrear-axle-drive gear 76 fixed on second counter shaft 71 constantlyengages with a second rear-axle-drive gear 77 fixed on third countershaft 72, thereby driving second-axle-differential 89 differentiallyconnecting rear axles 8 with each other. As a result, a part of thetorque of counter shaft 41 shared by center differential 23′ istransmitted to middle axles 25 and rear axles 8, and the remainder istransmitted to front axles 11 (while the front clutch is engaged).

[0086] The fifth embodiment employs a similar control system as shown inFIG. 11 so that, when brake pedal 19 is depressed, the front clutchincluding front clutch slider 96 is engaged and both center differential23′ and main-axle-differential 32 are locked for effectively applyingbraking force to all wheels 9, 26 and 12 of vehicle 1. In thisembodiment, the main axle provided thereon with brake 22 is notnecessarily driven prior to center differenitial 23′ for braking allwheels 9, 26 and 12 because all axle-differentials 32, 89 and 99 aresynchronously driven and connected together by the locking of centerdifferential 23′ during braking.

[0087] Referring to a sixth embodiment shown in FIG. 14, a pair of PTOcasings 15″ are fixedly provided on middle axle housing 16 a, preferablyon opposite outer sides thereof. One PTO casing 15″ supports rear PTOshaft 82′ extending backward, and the other supports front PTO shaft 87′extending forward. Instead of shafts 71, 72 and 73, middle transaxledevice 16 of this embodiment is provided with coaxial first and seconddifferential output shafts 78 and 79. Center differential 23′ isinterposed between shafts 78 and 79, and ring gear 74 of centerdifferential 23′ constantly engages with gear 51 fixed on counter shaft41.

[0088] First differential output shaft 78 is extended into one of PTOcasings 15″ so as to engage with front PTO shaft 87′ though bevel gears.Second differential output shaft 79 is extended into the other of PTOcasings 15″ so as to engage with rear PTO shaft 82′ through bevel gears.A gear 80 is fixed on second differential output shaft 79 so as toconstantly engage with ring gear 53 of main-axle-differential 32differentially connecting middle axles 25 with each other.

[0089] Therefore, similarly with the fifth embodiment, centerdifferential 23′ distributively transmits a part of the torque ofcounter shaft 41 to front axles 11 through first differential outputshaft 78 and the remainder to middle and rear axles 25 and 8 throughsecond differential output shaft 79.

[0090] The sixth embodiment also employs the similar control systemshown in FIG. 11 so that, when brake pedal 19 is depressed, the frontclutch including front clutch slider 96 is engaged and both centerdifferential 23′ and main-axle-differential 32 are locked foreffectively applying braking force to all wheels 9, 26 and 12 of vehicle1.

[0091] Referring to a seventh embodiment shown in FIG. 15, middletransaxle device 16 is provided at its one outer side with one PTOcasing 15′ in which rear PTO shaft 82′ and front PTO shaft 87′ aredisposed coaxially with each other. In PTO casing 15′, centerdifferential 23 is interposed between rear PTO shaft 82′ and front PTOshaft 87′ so as to differentially connecting both shafts 82′ and 87′with each other.

[0092] In middle axle housing 16 a, a second counter shaft 65 isdisposed parallel to counter shaft 41. Output gear 51 is fixed on secondcounter shaft 65 so as to constantly engage with ring gear 53 ofmain-axle-differential 32. Counter shaft 41 and second counter shaft 65are extended into PTO casing 15′. In PTO casing 15′, a bevel gear 68fixed on counter shaft 41 constantly engages with a bevel ring gear 69fixed to differential casing 23 a of center differential 23. Centerdifferential locking clutch slider 88′ is axially slidably disposedaround front PTO shaft 87′ so as to engage with and disengage fromdifferential casing 23 a. Thus, center differential 23 distributivelytransmits a part of the torque of counter shaft 41 to front axles 11through front PTO shaft 87′ and the remainder to middle and rear axles25 and 8 through rear PTO shaft 82′.

[0093] The seventh embodiment also employs the similar control systemshown in FIG. 11 so that, when brake pedal 19 is depressed, the frontclutch including front clutch slider 96 is engaged and both centerdifferential 23 and main-axle-differential 32 are locked for effectivelyapplying braking force to all wheels 9, 26 and 12 of vehicle 1.

[0094] Alternatively, in each of the fourth to seventh embodiments, bothmiddle axles 25 may be provided thereon with respective brakes 22. Inthis case, similarly with the first and second embodiments, the forcedlocking of main-axle-differential 32 for effectively transmittingbraking force to both middle axles 25 is unnecessary when brake pedal 15is depressed.

[0095] In each of the first to seventh embodiments, brake 22 may bealternatively provided on a member such as counter shaft 41 prior tomain-axle-differential 32 or center differential 23 or 23′. In thiscase, main-axle-differential 32, when braking, is not necessarilylocked, however, it is preferably locked for effectively applying thebraking force onto both the main axles.

[0096] For further or other embodiments of the present invention thanthe above mentioned embodiments shown in the drawings, main differential23 may be disposed in front transaxle device 10 so as to receive powerfrom engine 3 prior to middle and rear transaxle devices 16 and 4. Inthis case, input means of middle and rear transaxle devices 16 and 4 maysynchronously interlock with the primary side of one-way clutch 20, andfront (steering) axle 11 may synchronously interlock with the secondaryside of one-way clutch 20. Alternatively, input means of middle and reartransaxle devices 16 and 4 may synchronously interlock with one ofdifferential side gears 23 d of center differential 23, and front(steering) axle 11 may synchronously interlock with the otherdifferential side gear 23 d.

[0097] Although the invention has been described in its preferred formwith a certain degree of particularity, it is understood that thepresent disclosure of the preferred form has been changed in the detailsof construction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

What is claimed is:
 1. A multi-wheel-driving vehicle, comprising: threeor more axles arranged in parallel along a longitudinal axis of saidvehicle, each of said axles provided on both ends thereof withrespective drive wheels, wherein one of said three or more axles is asteering axle provided with steerable drive wheels; a pair of first andsecond transmission members, wherein said steering axle synchronouslyinterlocks with said second transmission member, and wherein at leastone of the other axles synchronously interlocks with said firsttransmission member; and power dividing means interposed between saidfirst and second transmission members, wherein power is transmittedthrough said power dividing means between said first and secondtransmission members while said power dividing means permits adifference of rotary speed between said first and second transmissionmembers.
 2. The multi-wheel-driving vehicle as set forth in claim 1 ,wherein said first and second transmission members are a pair of shaftsdisposed coaxially with each other, and wherein said power dividingmeans is a one-way clutch interposed between said pair of shafts.
 3. Themulti-wheel-driving vehicle as set forth in claim 1 , wherein said powertransmitted through said power dividing means is directed from saidfirst transmission member to said second transmission member.
 4. Themulti-wheel-driving vehicle as set forth in claim 1 , wherein saidsteering axle is the frontmost axle of said three or more axles.
 5. Themulti-wheel-driving vehicle as set forth in claim 1 , wherein only saidsteering axle of said three or more axles synchronously interlocks withsaid second transmission member.
 6. The multi-wheel-driving vehicle asset forth in claim 5 , wherein said axles are three in total, andwherein the two axles other than said steering axle synchronouslyinterlock with said first transmission member.
 7. Themulti-wheel-driving vehicle as set forth in claim 1 , furthercomprising: a brake provided on one of said three or more axles; amanual brake-operating tool for operating said brake; and locking meansfor locking said first and second transmission members together,wherein, when said brake-operating tool is operated for braking, saidlocking means is automatically operated to lock said first and secondtransmission members together.
 8. The multi-wheel-driving vehicle as setforth in claim 7 , wherein said brake is a wet-type brake.
 9. Themulti-wheel-driving vehicle as set forth in claim 7 , wherein said oneaxle provided thereon with said brake is other than said steering axle.10. The multi-wheel-driving vehicle as set forth in claim 7 , whereinsaid axle provided thereon with said brake is divided into two halves,and wherein said brake is provided on one of said halves, furthercomprising: a differential differentially connecting said halves witheach other; and differential-locking means for locking said two halvestogether, wherein when said brake-operating tool is operated forbraking, said differential-locking means is automatically operated tolock said halves together.
 11. A multi-wheel-driving vehicle,comprising: three or more axles arranged in parallel along alongitudinal axis of said vehicle, each of said axles provided on bothends thereof with respective drive wheels, wherein one of said three ormore axles is a steering axle provided with steerable drive wheels; andpower dividing means including an input member and a pair of outputmembers, said power dividing means differentially sharing powertransmitted into said input member between said pair of output members,wherein each of said input member and said pair of output memberssynchronously interlocks with at least one of said three or more axles.12. The multi-wheel-driving vehicle as set forth in claim 11 , whereinsaid power dividing means is a differential gear unit, and wherein saidpair of output members are a pair of coaxial shafts provided thereonwith respective differential side gears.
 13. The multi-wheel-drivingvehicle as set forth in claim 11 , wherein said steering axle is thefrontmost axle of said three or more axles.
 14. The multi-wheel-drivingvehicle as set forth in claim 11 , wherein only said steering axle ofsaid three or more axles synchronously interlocks with one of said inputmember and said pair of output members.
 15. The multi-wheel-drivingvehicle as set forth in claim 14 , wherein said axles are three intotal, and wherein the two axles other than said steering axlerespectively synchronously interlock with the other two of said inputmember and said pair of output members.
 16. The multi-wheel-drivingvehicle as set forth in claim 14 , wherein said steering axlesynchronously interlocks with one of said output members.
 17. Themulti-wheel-driving vehicle as set forth in claim 16 , wherein only saidsteering axle of said three or more axles synchronously interlocks withsaid one output member.
 18. The multi-wheel-driving vehicle as set forthin claim 17 , wherein said axles are three in total, and wherein the twoaxles other than said steering axle respectively synchronously interlockwith said input member and the other output member.
 19. Themulti-wheel-driving vehicle as set forth in claim 11 , furthercomprising: a brake provided on one of said at least three axles; amanual brake-operating tool for operating said brake; and locking meansfor locking said pair of output members together, wherein, when saidbrake-operating tool is operated for braking, said locking means isautomatically operated to lock said pair of output members together. 20.The multi-wheel-driving vehicle as set forth in claim 19 , wherein saidbrake is a wet-type brake.
 21. The multi-wheel-driving vehicle as setforth in claim 19 , wherein said one axle provided thereon with saidbrake is other than said steering axle.
 22. The multi-wheel-drivingvehicle as set forth in claim 19 , wherein said axle provided thereonwith said brake is divided into two halves, and wherein said brake isprovided on one of said halves, further comprising: a differentialdifferentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.
 23. A multi-wheel-driving vehicle, comprising: three or moreaxles arranged in parallel along a longitudinal axis of said vehicle,each of said axles provided on both ends thereof with respective drivewheels, wherein one of said three or more axles is a steering axleprovided with steerable drive wheels; and power dividing means includingan input member and a pair of output members, said power dividing meansdifferentially sharing power transmitted into said input member betweensaid pair of output members, wherein each of said three or more axlessynchronously interlocks with either of said output members so that eachof said output members synchronously interlocks with at least one ofsaid axles.
 24. The multi-wheel-driving vehicle as set forth in claim 23, wherein said power dividing means is a differential gear unit, andwherein said pair of output members are a pair of coaxial shaftsprovided thereon with respective differential side gears.
 25. Themulti-wheel-driving vehicle as set forth in claim 23 , wherein saidsteering axle is the frontmost axles of said three or more axles. 26.The multi-wheel-driving vehicle as set forth in claim 23 , wherein onlysaid steering axle of said three or more axles synchronously interlockswith one of said output members.
 27. The multi-wheel-driving vehicle asset forth in claim 26 , wherein said axles are three in total, andwherein the two axles other than said steering axle synchronouslyinterlock with the other output member.
 28. The multi-wheel-drivingvehicle as set forth in claim 23 , further comprising: a brake providedon one of said at least three axles; a manual brake-operating tool foroperating said brake; and locking means for locking said first andsecond output members together, wherein, when said brake-operating toolis operated for braking, said locking means is automatically operated tolock said first and second output members together.
 29. Themulti-wheel-driving vehicle as set forth in claim 28 , wherein saidbrake is a wet-type brake.
 30. The multi-wheel-driving vehicle as setforth in claim 28 , wherein said one axle provided thereon with saidbrake is other than said steering axle.
 31. The multi-wheel-drivingvehicle as set forth in claim 28 , wherein said axle provided thereonwith said brake is divided into two halves, and wherein said brake isprovided on one of said halves, further comprising: a differentialdifferentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.
 32. A multi-wheel-driving vehicle, comprising: a prime mover;three or more transaxle devices disposed in tandem along a longitudinalaxis of said vehicle, wherein each of said transaxle devices includesinput means and an axle serving as output means, said axle beingprovided on both ends thereof with respective drive wheels, wherein oneof said three or more transaxle devices is a main transaxle device whoseinput means receives power from said prime mover prior to the othertransaxle devices, and wherein one of said three or more transaxledevices is a steering transaxle device whose axle is provided withsteerable drive wheels; a pair of first and second transmission members,wherein power of said prime mover is taken out from said main transaxledevice to said first transmission member, and wherein said secondtransmission member synchronously interlocks with at least one of saidinput means of the other transaxle devices other than said maintransaxle device; and power dividing means interposed between said pairof transmission members, wherein said power is transmitted through saidpower dividing means from said first transmission member to said secondtransmission member while said power dividing means permits a differenceof rotary speed between said first and second transmission members. 33.The multi-wheel-driving vehicle as set forth in claim 32 , wherein saidfirst and second transmission members are a pair of shafts disposedcoaxially with each other, and wherein said power dividing means is aone-way clutch interposed between said pair of shafts.
 34. Themulti-wheel-driving vehicle as set forth in claim 32 , wherein saidsteering transaxle device is the frontmost transaxle device of saidthree or more transaxle devices.
 35. The multi-wheel-driving vehicle asset forth in claim 32 , wherein only said axle of said steeringtransaxle device of said axles of said three or more transaxle devicessynchronously interlocks with one of said first and second transmissionmembers.
 36. The multi-wheel-driving vehicle as set forth in claim 32 ,wherein said steering transaxle device is other than said main transaxledevice so that said input means of said steering transaxle devicesynchronously interlocks with said second transmission member.
 37. Themulti-wheel-driving vehicle as set forth in claim 36 , wherein only saidaxle of said steering transaxle device of said axles of said three ormore transaxle devices synchronously interlocks with said secondtransmission members.
 38. The multi-wheel-driving vehicle as set forthin claim 37 , wherein said transaxle device are three in total, andwherein said axles of the two transaxle devices other than said steeringtransaxle device synchronously interlock with said first transmissionmember.
 39. The multi-wheel-driving vehicle as set forth in claim 32 ,further comprising: a continuous variable transmission interposedbetween said prime mover and said input means of said main transaxledevice.
 40. The multi-wheel-driving vehicle as set forth in claim 39 ,further comprising: a power-take-out portion for transmitting power tosaid first transmission member provided on an opposite side of said maintransaxle device to said input means of said main transaxle device. 41.The multi-wheel-driving vehicle as set forth in claim 32 , furthercomprising: a brake provided on a transmission system or said axle insaid main transaxle device; a manual brake-operating tool for operatingsaid brake; and locking means for locking said input member and saidpair of output members of said power dividing means together, wherein,when said brake-operating tool is operated for braking, said lockingmeans is automatically operated to lock said input member and saidoutput members together.
 42. The multi-wheel-driving vehicle as setforth in claim 41 , wherein said brake is a wet-type brake.
 43. Themulti-wheel-driving vehicle as set forth in claim 41 , wherein said maintransaxle device is other than said steering transaxle device.
 44. Themulti-wheel-driving vehicle as set forth in claim 41 , wherein said axleprovided thereon with said brake is divided into two halves, and whereinsaid brake is provided on one of said halves, further comprising: adifferential differentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.
 45. A multi-wheel-driving vehicle, comprising: a prime mover;three or more transaxle devices disposed in tandem along a longitudinalaxis of said vehicle, wherein each of said transaxle devices includesinput means and an axle serving as output means, said axle beingprovided on both ends thereof with respective drive wheels, wherein oneof said three or more transaxle devices is a main transaxle device whoseinput means receives power from said prime mover prior to the othertransaxle devices, and wherein one of said three or more transaxledevices is a steering transaxle device whose axle is provided withsteerable drive wheels; and power dividing means including an inputmember and a pair of output members, said power dividing meansdifferentially sharing power transmitted into said input member betweensaid pair of output members, wherein each of all said input member andsaid pair of output members synchronously interlocks with at least oneof all said axle of said main transaxle device and said input means ofthe transaxle devices other than said main transaxle device.
 46. Themulti-wheel-driving vehicle as set forth in claim 45 , wherein saidpower dividing means is a differential gear unit, and wherein said pairof output members are a pair of coaxial shafts provided thereon withrespective differential side gears.
 47. The multi-wheel-driving vehicleas set forth in claim 45 , wherein said steering transaxle device is thefrontmost transaxle device of said three or more transaxle devices. 48.The multi-wheel-driving vehicle as set forth in claim 45 , wherein onlysaid axle of said steering transaxle device of said axles of said threeor more transaxle devices synchronously interlocks with one of saidinput member and said output members of said power dividing means. 49.The multi-wheel-driving vehicle as set forth in claim 45 , wherein saidsteering transaxle device is other than said main transaxle device sothat said input means of said steering transaxle device synchronouslyinterlocks with one of said output members of said power dividing means.50. The multi-wheel-driving vehicle as set forth in claim 49 , whereinonly said axle of said steering transaxle device synchronouslyinterlocks with said one output member of said power dividing means. 51.The multi-wheel-driving vehicle as set forth in claim 50 , wherein saidtransaxle device are three in total, wherein said axle of said maintransaxle device synchronously interlocks with said input member of saidpower dividing means, and wherein said input means of the transaxledevice other than said main transaxle device and said steering transaxledevice synchronously interlocks with the other output member of saidpower dividing means.
 52. The multi-wheel-driving vehicle as set forthin claim 45 , further comprising: a continuous variable transmissioninterposed between said prime mover and said input means of said maintransaxle device.
 53. The multi-wheel-driving vehicle as set forth inclaim 52 , further comprising: a power-take-out portion for transmittingpower to said first transmission member provided on an opposite side ofsaid main transaxle device to said input means of said transaxle device.54. The multi-wheel-driving vehicle as set forth in claim 45 , furthercomprising: a brake provided on a transmission system or said axle insaid main transaxle device; a manual brake-operating tool for operatingsaid brake; and locking means for locking said input member and saidpair of output members of said power dividing means together, wherein,when said brake-operating tool is operated for braking, said lockingmeans is automatically operated to lock said input member and said pairof output members together.
 55. The multi-wheel-driving vehicle as setforth in claim 54 , wherein said brake is a wet-type brake.
 56. Themulti-wheel-driving vehicle as set forth in claim 54 , wherein said maintransaxle device is other than said steering transaxle device.
 57. Themulti-wheel-driving vehicle as set forth in claim 54 , wherein said axleprovided thereon with said brake is divided into two halves, and whereinsaid brake is provided on one of said halves, further comprising: adifferential differentially connecting said halves with each other; anddifferential-locking means for locking said two halves together, whereinwhen said brake-operating tool is operated for braking, saiddifferential-locking means is automatically operated to lock said halvestogether.